For many years, fire hydrants have been constructed with their barrels made in two sections, an upper section and a lower section, the two sections being detachably connected to one another by frangible means which were normally positioned just above ground level. The lower barrel section, which had the major portion thereof buried, was connected to the hydrant shoe and usually the hydrant shoe was provided with a hydrant valve seat assembly threadably supported in the hydrant shoe. Some other prior constructions provided for the hydrant valve seat assembly being supported in the lower barrel section of the hydrant while in still other constructions the hydrant valve seat assembly was sandwiched between the hydrant barrel and the hydrant shoe but was connected both to the hydrant barrel and to the hydrant shoe so that it could not be retained with one or the other of the two elements mentioned when they were disassembled.
The difficulty with these prior hydrant constructions occurred when it was desirable to remove and replace a hydrant barrel from a hydrant shoe after the hydrant had been installed in a water distributor system or when a distributor wanted to remove a shoe from a hydrant and replace the shoe with another shoe having a different inlet configuration adaptable for a particular installation.
In installing hydrants, it is the usual practice to bury the lower portion of the hydrant to a bury line provided on the barrel of the hydrant. This positions the frangible connection between the lower barrel section and the upper barrel section of the hydrant at a location just above ground level. When a proper installation of a hydrant is accomplished, and the hydrant is subsequently struck by an automobile it is merely necessary to replace the upper hydrant barrel section without disturbing the lower barrel section or the hydrant shoe. However, as is often the case, hydrants are not properly installed and in some instances the frangible connection between upper and lower barrel sections is positioned too high above the ground during installation of the hydrant. With this type of installation, oftentimes the under carriage of a vehicle will hit and damage the lower barrel section necessitating replacement of the same along with possible replacement of the upper barrel section. In situations where the hydrant valve seat assembly was sandwiched between the lower barrel section and the hydrant shoe and held in place by both elements, it was necessary to turn off the water to the hydrant upstream of the same before repairs could be made as the hydrant valve seat assembly and valve element were not longer in place when the lower barrel section was removed from the shoe. Some prior art designs avoided this condition by threading or attaching the hydrant valve seat assembly directly to the hydrant shoe, but such an arrangement limited the interchangeability of a hydrant shoe from a hydrant barrel by the distributor when the necessity arose to change the hydrant shoe to provide a particular shoe inlet for a particular installation. The distributor not only had to remove the shoe from the hydrant barrel but also the hydrant valve seat assembly from the shoe if the same hydrant valve assembly was to be used in the reassembled hydrant. If this arrangement wasn't desirable, it meant the distributor had to stock each hydrant shoe having a different inlet size with a hydrant valve seat assembly and thus his inventory of shoes costs greater than if just the shoes by themselves were stocked.
For many years fire hydrants of the "dry" barrel type have been provided with drain valves for draining the hydrant barrel when the main hydrant valve is in the closed-position. These drain valves in the hydrants usually consisted of a drain passage from the exterior of the hydrant through the barrel or shoe and/or the valve seat assembly opening to the interior of the barrel at a point above the main hydrant valve. A leather strip carried by the moveable main valve element of the hydrant was arranged to close the opening of the drain passage when the valve element was moved to the open position. While the leather drain valve facing strips have given a somewhat satisfactory service, they did have the disadvantage of deteriorating in time and leaking after a certain number of cycles of operation. Efforts have been made more recently to improve the drain valve facing strips and in this respect rubber drain valve facing strips have been used. However, the rubber strips also have a disadvantage of "cold" flow and of deterioration from age.
In prior constructions of hydrants having drain valve passages therein, usually a portion of the passage was through the cast iron hydrant shoe or lower barrel section depending upon its location. The cast iron passage often corroded after a period of time and blocked the drain passage thus rendering the same useless.
In other prior constructions of hydrants, the hydrant seat ring was usually made of brass and was externally threaded so that it could be received in internal threads provided in the hydrant shoe or the hydrant lower barrel section. Since the lower barrel section or the shoe are made of cast iron, the cast iron threads of these elements would be mating with brass threads of the valve seat ring. Consequently, due to corrosion of the cast iron in time, the removal of the valve seat ring was made difficult.